The present invention relates to a cathode arc source, in particular to a cathode arc source adapted for industrial or long term operation.
Cathode arc deposition of tetrahedral amorphous carbon, metallic, dielectric and other such coatings is known in the art and offers the potential for deposition of thin films of high quality. Applications in scratch resistant optical coatings and hard disc media coatings are but two of a wide range of proposed uses.
Hitherto, deposition of films by the cathode arc process has been mainly limited to laboratory use, in general because of difficulties in the art in reliably depositing films that are free of or have acceptably low contamination by macroparticles--large, neutral particles.
Provision of improved means for filtering macroparticles from the arc plasma has recently been described in WO-A-96/26531 and also in as yet unpublished International patent application no. PCT/GB97/01992.
Existing filtered cathode arc sources can not yet, however, be continuously used, or used for long periods of time. This renders them unattractive for use in industrial processes. Existing cathode arc sources have to be shut down frequently so as to change or adjust or tidy up the target--this is time-consuming and wastes energy in reestablishment of the vacuum in the chamber and reestablishment of the arc. Whenever an arc is stopped and then restruck, the first plasma discharge from the arc is typically dirty and should preferably not be used for deposition on the substrate. Thus, when the arc is frequently stopped and restarted much operator interaction is required to obtain the best possible coating quality.
In use of known cathode arc sources, it is observed that target erosion is typically uneven, with the cathode spot moving erratically across the target surface. A relatively smooth target surface is preferred for deposition of plasma using a cathode arc source, but the smooth surface is rapidly lost by action of the arc spot.
Shutting down the arc and opening the chamber, including breaking vacuum in the chamber, in order to adjust or clean the target is undesirable for the reasons explained above.